Davide Italiano
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c8a7913f23
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[SimplifyLibCalls] Add a new transformation: pow(exp(x), y) -> exp(x*y)
This one is enabled only under -ffast-math (due to rounding/overflows)
but allows us to emit shorter code.
Before (on FreeBSD x86-64):
4007f0: 50 push %rax
4007f1: f2 0f 11 0c 24 movsd %xmm1,(%rsp)
4007f6: e8 75 fd ff ff callq 400570 <exp2@plt>
4007fb: f2 0f 10 0c 24 movsd (%rsp),%xmm1
400800: 58 pop %rax
400801: e9 7a fd ff ff jmpq 400580 <pow@plt>
400806: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1)
40080d: 00 00 00
After:
4007b0: f2 0f 59 c1 mulsd %xmm1,%xmm0
4007b4: e9 87 fd ff ff jmpq 400540 <exp2@plt>
4007b9: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
Differential Revision: http://reviews.llvm.org/D14045
llvm-svn: 251976
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2015-11-03 20:32:23 +00:00 |